UNiraAJT SOCIETY OF LONDON. xlix 



Tropical Africa, to which I called your attention in my paper on 

 Compositae, there are various considerations, requiring too much 

 detail for me now to enter upon them, tending to show a greater 

 probability of an ancient interchange having taken place far south 

 of the tropics, or eastward over lands long since submerged, than 

 across the Tropical Atlantic, A prevailing eastern element in the 

 Tropical- African flora has, indeed, been frequently pointed out. An 

 interchange with Continental India is so well marked north of the 

 equator as to have been generally admitted : but south there are 

 many distinct types represented only in Madagascar, Ceylon, Ma- 

 lacca, the Archipelago, or Australia. This would lead one into 

 speculations, put forward also by naturalists in other branches, as to 

 a vast continent once bridging ovet the Indian Ocean, and extend- 

 ing even far to the eastward into the Southern Pacific. Similar 

 views derived from zoology have been recently put forward by Gran- 

 didier, in a most interesting sketch of the physical geography and 

 natural history. of Madagascar, contained in u. 46 (May 11) of this 

 ., year's ' Eevue Scientifique.' This island, whose evident antiquity 

 and long isolation, aided by its broken surface, has enabled it to 

 become the seat or centre of preservation of a very large number oi 

 endemic monotypes, shows also in its vegetation, besides African, 

 many Archipelago and even Australian types. Grandidier believes 

 that in zoology the more distant eastern connexion is at least as 

 evident, if not more so than that with the almost adjacent African 

 continent. In plants, the African connexion is decidedly predo- 

 minant. 



I shall not attempt to follow Grisebach in discussing the peculia- 

 rities of the remainder of his regions. We may observe throughout 

 the same careful investigation of the climatic conditions and its in- 

 fluence on the vegetative character of the individual plants (Vege- 

 tationsformen) and on the general aspect of the whole vegetation 

 they constitute (Yegetationsformationen), with the same high esti- 

 mate or, we might say, overestimate of its efi'ects on the typical 

 character of the species as compared with the complicated con- 

 sequences of previous possession, foreign invasion, and natural selec- 

 tion in the struggle for life (which he seems disposed to ignore), and 

 with the same allusions to certain mysterious creative or productive 

 forces beyond the reach of our inquiries. A closer examination of 

 his regions shows them to be much better conceived in his phyto- 

 climatic point of view than I had at first thought them to be when 

 regarded as phyto-geographical regions; and although fvirther ex- 

 plorations may cause him to modify their limits in several instances, 



LiiTN. Peoc. — Session 1871-72. g 



